This invention relates to an improved torque controlled fluid shut-off and reset mechanism for a fluid operated tool.
Fluid operated tools for driving fasteners and the like typically incorporate a rotary vane air motor to drive a rotary output shaft connected to a tool bit. Such tools are often equipped with a clutch mechanism that responds to the torque imparted by the tool onto a fastener. When a specific torque is reached, the clutch mechanism automatically decouples the motor from the tool bit and terminates further tool output to the fastener. Further, in such tools, starting the tool is often effected by positioning the tool bit against the fastener and axially translating the bit holder by pushing it against the fastener. Axial translation then opens a fluid valve to the air motor for the tool.
Combining a start-up control, torque control as well as a shut-off control mechanism in a single tool is a desirable goal and various tools include such combinations. Prior art references which disclose devices of this general nature include U.S. Pat. No. 4,576,270 issued Mar. 18, 1986, for a torque control and fluid shut-off mechanism for a fluid operated tool. Equally relevant is U.S. Pat. No. 4,880,064, entitled "Torque Sensing Automatic Shut-off And Reset Clutch For Screwdrivers, Nutsetters and The Like", issued on Nov. 14, 1989. U.S. Pat. No. 4,880,064 is incorporated herewith by reference. This patent teaches the use of a torque control and fluid shut-off mechanism for a fluid operated tool which includes a bit holder and a driving clutch member which are connected so as to uniformly and co-jointly move in an axial direction independent of rotary movement associated with rotary output of the air motor. Spring biased ball bearings provide for co-joint rotary movement which terminates when the spring biasing force is associated with the driving clutch member exceeds a threshold level so as to cause the ball bearings to disengage from a bit holder. A locking sleeve is fitted over the driving clutch member and cooperates with a control rod for fluid inlet to the rotary vane air motor. This arrangement controls initiation of operation, termination of operation and resetting of the tool.
The present invention comprises an improvement with respect to the subject matter of U.S. Pat. No. 4,880,064. More specifically the present invention relates to an improved construction of the ball bearing connection between the clutch members and bit holder. Additional improved features are also disclosed.